Small (mostly) to medium agaric, growing on litter or mulch, wood or bryophytes, with a white or cream to yellow spore print. Pileus white, pale, yellow, orange, brown, grey, rarely red or pink, green, purple, blue or black, dry or moist, viscid or glutinous. Lamellae adnexed, adnate, subdecurrent, decurrent, rarely free or sinuate or notched. Stipe central. Partial veil remnants absent. Spores hyaline, amyloid or non-amyloid, smooth; germ pore absent. Cheilocystidia present. Lamellar trama regular. Pileipellis a cutis; consisting of filamentous hyphae that are distinctly nodulose. Clamp connections present, rarely absent.

Other identification units of Mycena include distinctive species or sections such as M. cystidiosa (with large thick-walled pileocystidia with apical horns, in combination with criniform stipes), M. leaiana (with bright orange lamellae, combined with a viscid to glutinous pileus and stipe), M. nargan (with white squamules on the pileus when young), section Adonideae (with non-amyloid spores), section Calodontes (more robust species with pink or purple pileus colours, and pileipellis hyphae that are only rarely nodulose) and section Sacchariferae (with acanthocysts in the pileipellis). Roridomyces (previously included in Mycena as section Roridae) has a hymeniderm pileipellis. Cruentomycena (previously included in Mycena as section Viscidocruentae) is very similar macroscopically, but it combines viscid pileus and stipe with smooth pileipellis hyphae. The rarely seen genus Mycenella is also very similar macroscopically, but it differs in the spores with nodulose warts. Among other white-spored agarics on wood or litter with smooth spores, Marasmius can be similar in stature but it has a tough texture, the stipe is often black below and pale above, spores are non-amyloid and the pileipellis is a hymeniderm; Gymnopus has non-amyloid spores; and Hiemiella and Xeromphalina (which do have amyloid spores) are rather tough in texture, and usually have either a trichoderm (in the former) and a pileipellis with smooth hyphae (in the latter). Some brown-spored genera, such as Galerina and Conocybe, closely resemble Mycena in the field, but have brown spore prints.

Sixty species in 21 sections are accepted by Grgurinovic (2002) in her monograph of the genus in south-eastern Australia. Further species are expected outside of this area, particularly in northern Australia.

Six sections are keyed out separately in FunKey because their species are highly distinctive, or else by treating the sections separately, the remaining sections are more uniform in the diagnostic characters. Sections keyed out separately are: Adonideae (two species), Caespitosae (M. leaniana), Calodontes (four species), Metuloidiferae (M. cystidiosa), Nargan (M. nargan), and Sacchariferae (six species).

Two of the sections of Mycena accepted by Grgurinovic (2002) are now treated as separate genera: section Viscidocruentae as Cruentomycena and section Roridae as Roridomyces.

The remaining sections keyed out as Mycena (other) are:

Section Cinerellae (cheilocystidia clavate, with coarse protuberances): M. mijoi, M. nivalis and M. subvulgaris.

Section Clavulares (stipe with a basal disc): M. subalbida (subglobose spores).

Section Cyanocephalae (blue pileus, stipe with a basal disc): M. interrupta.

Section Filipides (cheilocystidia usually with evenly spaced protuberances): M. austrofilopes (with var. roseobrunnea).

Section Fragilipedes (cheilocystidia smooth or with few, coarse protuberances): M. albidofusca (with a distinct pale spot in the pileus centre), M. atrata, M. atroavellanea, M. australiana, M. fuhreri, M. fusca, M. lilliria, M. kyeema (unusual in having a combination of smooth pileipellis hyphae and the absence of clamp connections), M. lageniformis, M. marangania, M. simpsonii, M. subgalericulata (name often used in a broad sense in Australian literature), M. tallangattensis, M. trachycephala, M. tuvara and M. waralya.

Section Galactopoda (with blood-red latex): M. insueta, M. kuurkacea (= M. sanguinolenta in the sense of Australian authors) and M. toyerlaricola.

Section Hygrocyboideae (pileus and stipe viscid, the stipe usually yellow; members of this section have been referred to as M. epipterygia in Australian literature): M. murna, M. nyula, M. tasmaniensis and M. tuuwuulensis.

Section Lactipides (white or watery latex): M. neerimensis and M. thunderboltensis.

Section Maldae (pileus small, pale, stipe and pileus not viscid, criniform stipes present): M. maldea.

Section Mulawaestres (pileus brown, pileus and stipe glutinous, lamellar edge brown): M. mulawaestris.

Section Mycena (Australian species often with smooth pileipellis hyphae): M. austromaculata, M. cunninghamiana, M. eucalyptorum, M. subnigra and M. yuulongicola.

Section Polyadelphia (stipe arising from a basal patch of mycelium or radiating fibrils): M. albidocapillaris (= M. subcapillaris).

Section Rubromarginatae: M. kurramulla (lamellae adnate with a decurrent tooth to subdecurrent, edge red).

W.A., S.A., Qld, N.S.W., Vic. and Tas. (and probably also N.T.).

In native forests and in gardens and pine plantations.

On standing trees or fallen wood or litter.

Saprotrophic.

Bougher, N.L. (2009a), Fungi of the Perth region and beyond: a self-managed field book, Western Australian Naturalists' Club (Inc.), Perth. [Description and Illustration of M. kuurkacea and M. subgalericulata]

Bougher, N.L. & Syme, K. (1998), Fungi of Southern Australia. University of Western Australia Press, Nedlands. [Description, Illustration and Microcharacters of M. subgalericulata]

Fuhrer, B. (2005), A Field Guide to Australian Fungi. Bloomings Books, Hawthorn. [Description and Illustration of M. albidocapillaris, M. albidofusca, M. aff. atrata, M. austrofilopes, M. aff. epipterygia, M. interrupta, M. kurramulla, M. kuurkacea, M. maldea, M. marangania, M. mijoi, M. mulawaestris, M. nivalis, M. subgalericulata, M. subvulgaris, M. toyerlaricola, M. yuulongicola and several unnamed species]

Fuhrer, B. & Robinson, R. (1992), Rainforest Fungi of Tasmania and South-east Australia. CSIRO Press, East Melbourne. [Illustration of M. epipterygia, M. interrupta, M. albidocapillaris (as M. subcapillaris) and an unnamed species]

Grey, P. & Grey, E. (2005), Fungi Down Under. Fungimap, South Yarra. [Description, Illustration and Map for M. interrupta]

Grgurinovic, C.A. (1997a), Larger Fungi of South Australia. The Botanic Gardens of Adelaide and State Herbarium and The Flora and Fauna of South Australia Handbooks Committee, Adelaide. [Key to South Australian species and Description and Microcharacters of M. albidocapillaris, M. albidofusca, M. australiana, M. austrofilopes, M. austromaculata, M. cunninghamiana, M. eucalyptorum, M. fusca, M. kurramulla, M. kuurkacea group ( as M. sanguinolenta), M. kyeema, M. lilliria, M. marangania, M. maldea, M. nyula, M. subalbida, M. subgalericulata, M. subnigra, M. subvulgaris and M. waralya, and Illustration of M. albidofusca, M. cunninghamiana, M. kurramulla and M. kuurkacea group (as M. sanguinolenta)]

Grgurinovic, C.A. (2003), The genus Mycena in south-eastern Australia. Fungal Diversity Press, Hong Kong and Australian Biological Resources Study, Canberra. [Comprehenisve monograph inlcuding Description and Microcharacters for and Key to 61 Australian species of Mycena, along with B&W Illustration of most species, and Illustration of about half the species]

McCann, I.R. (2003), Australian Fungi Illustrated. Macdown Productions, Vermont. [Illustration of M. albidofusca, M. epipterygia, M. interrupta, M. kuurkacea group (as M. sanguinolenta) and several unnamed species]

Young, A.M. (2005b), A Field Guide to the Fungi of Australia. University of New South Wales Press, Sydney. [Description and Illustration of M. interrupta, and Description and B&W Illustration of M. epipterygia, M. kuurkacea group (as M. sanguinolenta) and M. subgalericulata]